Fan blade construction



L. A. MYERS June 6, 1967 FAN BLADE CONSTRUCT ION 2 Sheets-Sheet 1 Filed Aug.

June 6, 1967 MYERS 3,323,711

FAN BLADE CONSTRUCT I ON Filed Aug. 5, 1965 2 Sheets-Sheet 2 J1; 207 67266 (5. ens @fiwd, M wmwihg United States Patent 3,323,711 FAN BLADE CONSTRUCTIUN Lawrence A. Myers, Milford, Ind., assignor to Chore- Time Equipment, Inc, Milford, Ind, a corporation of Indiana Filed Aug. 5, 1965, Ser. No. 477,474 3 Claims. (Cl. 230-134) ABSTRACT OF THE DISCLOSURE The present invention relates to a novel ventilating apparatus, and more specifically to a novel ventilating fan structure. The disclosed embodiment of the invention comprises fan blade elements which are formed by extruding and which are secured to a hub member by means of extruded mounting brackets positioning the blades at a predetermined pitch with respect to the hub member.

In general, ventilating fans have heretofore been provided with blade structures formed either from a casting or from sheet metal stampings attached to a hub member. Of these two constructions, it is usually possible to make a cast blade so as to have the most efiicient shape. However, such cast blades are expensive and require the exercise of great skill and care in the initial casting and also in the final finishing. Furthermore, such cast parts frequently are subject to warpage, and also include variations in the density of the cast material which require precision in both static and dynamic balancing.

In an attempt to overcome the expense and problems of cast blades, structures have been made wherein the individual blades are stamped from sheet metal and are attached to a hub. However such sheet metal stampings normally cannot be provided with the necessary shape for most efficient performance. Furthermore such sheet metal stampings frequently are incapable of having an adequate crosssection so as to obtain the necessary strengths for proper performance and durability.

It is an important object of the present invention to provide a novel fan blade construction having a relatively efilcient configuration and capable of being produced easily and economically.

A more specific object of the present invention is to provide a novel fan blade construction of relatively efficient configuration and which requires little or no final finishing or balancing of the blade elements.

Still another object of the present invention is to provide a novel fan blade construction of the above-described type which is relatively strong and durable.

A further object of the present invention is to provide a novel blade construction of the above-described type which may be readily adapted for utilizing different numbers of individual blade elements.

Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings wherein:

FIG. 1 is a back elevational view showing a ventilating fan incorporating features of the present invention;

FIG. 2 is a partial sectional view taken generally alon a line 2-2 in FIG. 1;

FIG. 3 is an enlarged fragmentary front elevational view showing a central portion of the blade construction in the fan of FIGS. 1 and 2;

FIG. 4 is a fragmentary sectional view taken generally along line 4-4 in FIG. 3;

FIG. 5 is a plan view of an individual blade element incorporated in the fan blade structure taken along line 5-5 in FIG. 4;

FIG. 6 is a perspective view showing a fitting or bracket incorporated in the fan blade construction for securing an individual blade element to a hub member;

FIG. 7 shows the cross-sectional configuration of the blade element along line 7-7 in FIG. 5;

FIG. 8 shows the cross-sectional configuration of the blade element along line 8-8 in FIG. 5; and

FIG. 9 shows the cross-sectional configuration of the blade element along both of lines 9-9 in FIG. 5.

Referring now more specifically to the drawings wherein like parts are designated by the same numerals throughout the various figures, a ventilating fan 10 incorporating features of the present invention is shown in FIGS. 1 and 2. The fan comprises a generally rectangular frame 12 having a circular opening 14 therethrough. The rectangular frame merges with a cylindrical guide section 16 which defines the opening or passageway 14.

An elongated sleeve and bearing assembly 18 is supported in axial alignment with the passageway or opening 14 by a plurality of braces 20 and 21 suitably secured to the frame 12. A shaft 22 is rotatably supported within the sleeve and bearing unit 18 for carrying a fan blade construction 24 incorporating features of the present invention and described in detail below. A driving motor 26 is mounted in association with the frame. The motor carries a pulley 28 on its shaft 30 for driving an endless belt 32 which in turn extends around and drives a pulley 34 fixed on the fan blade shaft 22.

As indicated in FIG. 1, the motor 26 is fixed to a mounting plate 36 which in turn is pivotally connected as at '38 to a bracket 40 fixed between a pair of the supporting braces 20 and 21. With this arrangement, the weight of the motor 2-6 is utilized for maintaining the desired tension in the drive belt 32.

The fan blade construction 24 comprises a plurality of individual blade elements 42 which are constructed as is described in detail below. The blade elements are attached to a central hubmember 44 with the aid of brackets 46.

The blade elements 42 are of identical construction, which construction is shown best in FIGS. 3-5 and 7-9. In order to produce the blade elements, a length of stock material is extruded from aluminum or other suitable material. This extrusion is formed with an airfoil crosssectional configuration. In the specific embodiment disclosed herein, the initial cross-sectional configuration of the extrusion is shown in FIG. 9 and is such that an airfoil is provided having a relatively thin leading and trailing marginal portions 48 and 5t respectively, a relatively thick intermediate portion 52, a concave surface 54 and an opposite convex surface 56. The extrusion process enables this particular and relatively efficient airfoil crosssectional configuration to be obtained with a high degree of accuracy. Furthermore, the extruded stock material is of substantially uniform shape and weight or density throughout its length and has a smooth surface finish so as to minimize or eliminate any need for subsequent finishing and balancing of individual blade elements. The extruded stock material also has high strength and is not subject to warpage.

After the blade stock material is extruded with the crosssectional configuration shown in FIG. 9, it is cut to provide sections having the desired length for the blade elements 42. The aluminum or other material of the extrusion is ductile and in order to increase the efficiency of the blade structure, the initial extrusions of the blade elements 42 are subjected to a reforming or stamping process for obtaining the final configuration shown best in FIGS. 5 and 7-9. More specifically, an inner end or shank portion 58 of the blade element 42 is left with the original extruded airfoil configuration and pitch while an immediately adjacent portion 60 of the blade element is formed so as to increase pitch and airfoil curvature as shown in FIGS. 5 and 8. The configuration of the blade progressively changes from adjacent a junction area 62 between the portions 58 and 60 so that the blade has substantially the original airfoil configuration and pitch at a location 64 about midway between the junction 62 and an outer end tip 66 of the blade as shown in FIGS. 5 and 9. The blade element is still further formed so that the airfoil and pitch are progressively increasingly flattened from the location 64 to an outer end portion 68 as shown in FIGS. 5 and 7.

The hub member 44 has a central section 70 with a bore therethrough for receiving the shaft 22. A disc 72 extends radially from the central section 7 0, which disc has a flat seat surface 74 for receiving the blade mounting bracket 46. A rearwardly extending annular flange 76 projects from a peripheral margin of the disc 72 for strengthening and rigidifying the disc, and, if desired, a similar flange 78 may be provided extending from an intermediate portion of the disc.

The blade element attaching brackets 46 are identical to each other and are preferably formed from extruded aluminum or other suitable material. The extrusion of the attaching brackets provides many of the same advantages mentioned above in connection with the blade elements.

As shown best in FIGS. 3, 4 and 6, each of the attaching brackets 46 has a main body portion 80 presenting a concave surface or seat 82 having the same configuration as the surface 56 of a blade element shank portion 58. A reversely extending flange 84 is joined to and overlies a forward margin of the body portion 80 for overlying a leading edge of a blade element as shown in FIG. 4. In order to support the body portion 80 at the desired angle with respect to the hub member, a foot section 86 is provided for abutting the fiat surface of the hub member, which foot section is joined to a trailing portion of the body 80 by a leg section 88. The leg section is, however, spaced substantially forwardly from the trailing edge of the body portion 80 so that the body portion, in effect, presents a flange 90 projecting rearwardly of the leg section 88.

In order to adapt the bracket 46 for attachment to the hub members, aligned fastener receiving apertures 92 and 84 are provided in the body portion 80 and flange 84 and additional apertures 96 and 98 are formed in the foot section 86. As shown in FIGS. 3 and 4, a fastener 100 such as a rivet or bolt is inserted through the apertures 92 and 94 and an aligned aperture in the hub member disc portion 72. Additional rivets or bolts 102 are inserted through the apertures 96 and 98 and the disc member so that the bracket 46 is secured to the hub member at three points.

As shown in FIG. 4, the fastener 100 not only serves to secure the bracket to the hub member, but also extends through an aperture 104 in the blade element for securing the blade to the bracket. In addition, apertures 106 and 108 are formed in the trailing flange section of the bracket for alignment with apertures 110 and 112 in the blade element. Additional fasteners 114 and 116 such as rivets or bolts are inserted through these aligned apertures for completing the connection of the blade element to the bracket.

In the embodiment shown herein, the fan blade structure 24 has four equally spaced blade elements 42. However, with the simple and uniform extruded blade elements and attachment brackets previously described, the number of blade elements in a blade structure or assembly may be easily varied and the hub member may be easily adapted for a difi'erent number of blades by simply changing the locations of the holes therein for receiving the fasteners 100 and 102,

While a preferred embodiment of the present invention has been shown and described herein, it is obvious that many structural details may be changed without departing from the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A fan blade construction comprising a central hub member, a plurality of generally radially extending blade elements, each of said blade elements having an airfoil cross-sectional configuration substantially throughout its length, said airfoil configuration having relatively thin leading and trailing marginal portions and a relatively thick central portion, each of said blade elements having a predetermined pitch at an inner end thereof and being formed with a varying pitch toward an outer end thereof, means attaching said blade elements to said hub member comprising an attachment bracket for each of said blade elements, each of said attachment brackets including a body portion presenting a seat surface conforming to an adjacent surface of its associated blade element, leading ends of said bracket body portions substantially abutting said hub member, each of said brackets including a foot means connected with a trailing portion of its body portion and engaging said hub member and positioning said body portion at said predetermined pitch with respect to said hub member.

2. A fan blade construction, as defined in claim 1, which includes fastener elements extending between said foot means and said hub member, additional fastener means extending through leading portions of each of said blade elements and said body portion associated therewith, and additional fastener elements extending between said trailing portion of each of said brackets and an associated blade element.

3. A fan blade construction comprising a plurality of longitudinally extruded blade elements of substantially uniform density throughout their lengths, said blade elements having an airfoil cross-sectional configuration initially uniform throughout their length, and means includ ing attachment brackets respectively associated with each of said blade elements for interconnecting the radially inner end portions of said blade elements, said attachment brackets being of longitudinally extruded material and having substantially uniform transverse cross-sectional configuration throughout their length, each of said brackets including a thin body portion presenting a seat conforming to its associated blade element, said body portion being disposed at a predetermined pitch, a reversely extending flange connected with a leading margin of each of said brackets and extending rearwardly over an associated blade element, and foot means extending from a trailing marginal section of each of said body portions for supporting the body portions at a predetermined pitch.

References Cited UNITED STATES PATENTS 1,319,634 10/1919 Whipps 169 1,454,356 5/ 1923 Walker 230134.2 1,869,802 8/1932 Dore 170-160.5 2,032,224 2/1936 Paton 103115 2,794,509 6/1957 Mix 170173 2,856,675 10/1958 Hansen 29156.83

FOREIGN PATENTS 614,074 8/ 1947 Great Britain.

DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. A FAN BLADE CONSTRUCTION COMPRISING A CENTRAL HUB MEMBER, A PLURALITY OF GENERALLY RADIALLY EXTENDING BLADE ELEMENTS, EACH OF SAID BLADE ELEMENTS HAVING AN AIRFOIL CROSS-SECTIONAL CONFIGURATION SUBSTANTIALLY THROUGHOUT ITS LENGTH, SAID AIRFOIL CONFIGURATION HAVING RELATIVELY THIN LEADING AND TRAILING MARGINAL PORTIONS AND A RELATIVELY THICK CENTRAL PORTION, EACH OF SAID BLADE ELEMENTS HAVING A PREDETERMINED PITCH AT AN INNER END THEREOF AND BEING FORMED WITH A VARYING PITCH TOWARD AN OUTER END THEREOF, MEANS ATTACHING SAID BLADE ELEMENTS TO SAID HUB MEMBER COMPRISING AN ATTACHMENT BRACKET FOR EACH OF SAID BLADE ELEMENTS, EACH OF SAID ATTACHMENT BRACKETS INCLUDING A BODY PORTION PRESENTING A SEAT SURFACE CONFORMING TO AN ADJACENT SURFACE OF ITS ASSOCIATED BLADE ELEMENT, LEADING ENDS OF SAID BRACKET BODY PORTIONS SUBSTANTIALLY ABUTTING SAID HUB MEMBER, EACH OF SAID BRACKETS INCLUDING A FOOT MEANS CONNECTED WITH A TRAILING PORTION OF ITS BODY PORTION AND ENGAGING SAID HUB MEMBER AND POSITIONING SAID BODY PORTION AT SAID PREDETERMINED PITCH WITH RESPECT TO SAID HUB MEMBER. 